Combination of convergent-beam electron diffraction and 1 MeV structure imaging in a structure determination of Na₂Ti₉O₁₉

The space group and atom configuration of monoclinic Na₂Ti₉O₁₉ have been studied by combining 1 MeV high-resolution electron microscope imaging with the convergent-beam electron diffraction (CBED) technique. The crystal has monoclinic symmetry with lattice parameters a = 12.2, b= 3.78, c = 15.6 Å and β= 105°. The space group was determined uniquely to be centrosymmetric C2/m by selecting the point group from the symmetry of the CBED pattern. On the basis of the 1 MeV structure-image observation reported previously and the space-group determination, the crystal structure of monoclinic Na₂Ti₉O₁₉ is proposed and atom coordinates are given.